Mobile scaffold



Dec. 12, 1967 'E. A. WAGNER 3,

MOBILE SCAFFOLD Filed Dec. 27, 1965 5 Sheets-Sheet 1 ELMER A. WAGNE R lNVE/VTOE BUC/(HOR/V, BLORE, KLAROU/ST 8 SPAR/(MAN ATTORNEYS Dec. 12, 1967 E. A. WAGNER 3, 7,

' MOBILE SCAFFOLD Filed Dec. 27, 1965 5 Sheets-Sheet 2 ELMER A. WAGNER INVE/VTU/P BUC/(HOR/V, BLORE, KL/IROU/ST 8 SPAR/(MAN Dec. 12, 1967 Filed Dec. 2'7, 1965 E. A. WAGNER MOBILE SCAFFOLD 3 Sheets-Sheet l;

FIG. 3

ELMER A. WAGNER lNVE/VTOI? BY BUG/(HORN, BLORE, KLAROU/ST 8 SPAR/(MAN ATTORNEYS United States Patent 3,357,517 MGBILE SCAFFOLD Elmer A. Wagner, Rte. 1, Box 120, Cornelius, Greg. 97113 Filed Dec. 27, 1965, Ser. No. 516,535 ltl Claims. (Cl. 182-2) This invention relates to a mobile scaffold and particularly to a transportable mobile scaffold for providing access to the underside of elevated surfaces.

Access to the underside of elevated surfaces such as bridges, elevated roadways and the like may be provided with conventional scaffolding suspended from the elevated structure. Access to a large area of such surface for construction, painting, inspection and repairing thereof, then involves the considerable expense of construction and reconstruction of the scaffolding and moving of such scaffolding from one location to another. Alternatively such an under surface may sometimes be reached with a conventional crane or other boom device. However, there may be no place where such a crane may be positioned, as in the case of uneven terrain or when an obstruction is present. Moreover, the elevated surface may be at too great a height for convenient access with a conventional crane device.

It is therefore an object of the present invention to provide a mobile scaffold apparatus for positioning and supporting an individual in difficult to reach locations.

It is another object of the present invention to provide an improved mobile scaflold apparatus for providing convenient, ready access to the underside of elevated surfaces.

Briefly, in accordance with an embodiment of the present invention, a mobile scaffold comprises a rotatable base member and a first boom for positioning an intermediate support means at the distance from the base member. The first boom includes a pair of parallel arms pivoted to the base member upon parallel axes, and the arms are similarly pivoted to the intermediate support means so the intermediate support means is maintained at a constant attitude with respect to the base member, e.g., with the intermediate support means maintained in a vertical position even though the boom is raised and lowered. The intermediate support means preferably includes a vertical shaft depending from the head end of the first boom and rotatable with respect to the first boom.

A second boom, pivoted from the lower end of the vertical shaft, similarly comprises a pair of parallel arms. The second boom supports a working bridge at its head end, and, since the second boom includes a parallel arm mechanism, the bridge is maintained at a constant attitude with respect to the base member, e.g., with its floor parallel to the floor or" the base member.

The base member may be located on the top of an elevated surface such as an elevated highway or the like with the first boom extending downwardly and over the side of the elevated structure. The second boom, rotatably attached to the end of the first, is conveniently swung into a position so it extends back under the elevated structure upon which the base member is located. The booms may be moved horizontally and vertically to position the bridge into a desired position under the elevated structure whereby an individual located on the bridge may obtain easy access to the structures under surface.

According to another feature of the present invention, the base member is desirably rotatably supported upon a vehicle. For example, the base member may comprise a cab mounted on the bed of a truck. For transporting the mobile scaffold according to the present invention,

the booms are swung over the bed of the truck with the second boom extending back under the first. Of course, the vehicle mounting also provides convenient movement of the scaffold while the same is in use, e.g., in inspecting extended lengths of an under surface.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like reference characters refer to like elements and in which:

FIG. 1 is a perspective view of a mobile scaffold according to the present invention in operating position,

FIG. 2 is a side view of the mobile scaffold according to the present invention in an extended position, and

FIG. 3 is a side view of the mobile scaffold according to the present invention mounted on the bed of a vehicle and shown in retracted position for transporting.

Referring to the drawings, a rotatable base member comprising a cab 10 supports an intermediate support member 12 by means of a first boom 14. A second boom 16 extends from the lower end of an intermediate support means 12 and in turn supports a bridge 18 to which may be connected bridge extension 20. The bridge 18 and bridge extension 29 are maintained in a substantially horizontal position and may be suitably positioned under an elevated roadway 22 for construction, inspection, painting, or the like, as illustrated in FIG. 1. In this illustration, the cab 10 is positioned atop roadway 22 and is rotatable about a vertical axis as will hereinafter become more evident.

Boom 14 comprises an upper arm 24, and a lower arm 26 substantially equal in length to arm 24, where the arms are disposed in parallel relation. Both arms 24 and 26 are pivoted at the upper front of cab 10 on parallel axes and swing vertically within an indented area 28 on the front side of the cab. Arm 26 is mounted for vertical rotation about a horizontal shaft 30 extending across the indented area 28 approximately midway up the front of cab 10. Arm 24 pivots in a vertical plane from brackets'32 located atop the, cab as seen more clearly in FIGS. 2 and 3. N

The opposite ends of arms 24 and 26 pivot in upper and lower bearings 34 and 36 establishing parallel axes and located within vertical side members 38 of intermediate support means 12. These vertical side members are joined with horizontal cross pieces 40 extending on either side of a vertical sleeve 42 to which the cross pieces are secured. Upper bearings 34 and lower bearings 36 in vertical side members 38 are spaced the same vertical distance apart as shaft 30 and the pivotal axis of arm 24 with respect to brackets 32. Thus arms 24 and 26 together with vertical side members 38 and cab 10 between the arms form a parallelogram or parallel motion system whereby side members 38 and sleeve 42 are maintained in substantially the same parallel attitude with respect to cab 14 That is, as the head end of boom 14 is raised and lowered with respect to cab 10, side members 38 and sleeve 42 are maintained in a vertical position.

Movement of boom 14 comprising arms 24 and 26 in a vertical direction is accomplished by means of a main hydraulic cylinder 44 pivoted at its lower end to engage a shaft 46 extending across the lower part of indented area 28 of cab 10. Actu-ating rod '50 of main cylinder 44 is pivotally secured to the top of bracing member 54 extending across arm 26.

Sleeve 42 of intermediate support means 12 is pro- 'vided near the top thereof with a thrust bearing for journaling a main shaft 56 maintained in a substantially vertical orientation within sleeve 42. Main shaft 56 depends from sleeve 42 and supports a second boom 16 comprising a lower arm 60 and an upper arm 62 of equal length.

A pair of parallel horizontal rods 64 are joined to the lower end of main shaft 56 on one side thereof and are vertically spaced with respect to one another, Arms 60 and 62 turn upon rods 64 and are arranged to extend from rods 64 toward the opposite side of the main shaft 56. The opposite ends of arms 60 and 62 are pivotally joined to a Working bridge 18 having brackets 68 pivotally receiving parallel end shafts joined to arms 60 and 62. Brackets 68 are positioned such that arms 60 and 62 are equi-spaced at both ends, in the same manner as the aforementioned arms 24 and 26, and since the arms 60 and 62 are also of equal length, bridge 18 is maintained in a parallel attitude with respect to intermediate support means 12 and therefore with respect to cab 10. That is, bridge 18 is maintained with side members 70 in a vertical position and its lower floor member 72 in a horizontal position.

A secondary cylinder 74 hinged to main shaft 56 at bracket 78 has its actuator rod 80 pivoted to the upper end of bracing member 82 extending across arm 62. Operation of cylinder 74 controls upward and downward movement of the boom 16 comprising arms 60 and 62. The boom 16 also rotates on main shaft 56. A hydraulic motor 84 supported from upper cross piece 40 initiates and controls therotation of the main shaft 56. Hydraulic motor 84 drives shaft 56 through a chain 86 engaging sprocket 88 which is in turn keyed to the shaft 56. Therefore, the boom 16 carried on the shaft 56 may be turned in any desired direction.

Although the bridge 18 is of sufficient size for many purposes, e.g., of sufficient size for. supporting one man, it is frequently desirable to lengthen the Working space thus available at the head end of the boom by means of an extension bridge 20. For joining extension to bridge 18, the bridge 18 is provided with brackets 90 carrying outwardly extensible pins, for conveniently engaging the adjacent end of the bridge extension 20. Thus extension 20 considerably lengthens the working space available at the head end of the boom as illustrated in FIG. 1. Since bridge extension 20 is securely joined to the bridge '18, bridge extension '20 is maintained in a substantially horizontal attitude despite changes in orientation and'direction of the various boom members.

For the purpose of strengthening the booms, at least one arm of each boom is preferably formed as a steel pipetruss frame. For example, arm 26 of boom 14 and arm 62 of boom 16 are so formed. The truss frames include both vertical struts and horizontal cross braces as can be seen from the FIG. 1 perspective drawing. Arm 26 desirably increases inits vertical dimension from each end toward the bracing member 54 where upward force is applied by means of actuating rod 50 of main cylinder 44, while arm 62 desirably employs A-frame truss side members. The remaining arms 24 and 60, are also desirably steel pipe structures and are at leastcross braced as shown in the FIG. 1 perspective drawing. To further reinforce boom 16, a vertical bracing member 92 is pivotally connected between the center of arm 60 and'the'center of arm 62. Since these points on arms 60 and 62 remain vertically separated by a constant distance, bracing members 92 remains in a vertical position and does not interfere with the operation of the apparatus.

The main cylinder 44 as well as a secondary cylinder 74 and hydrauhc motor 84 are operated and controlled in a conventional manner. 'A first or primary operating station thereforis located in cab 10. A desirable additional feature comprises a second operating station 94 located on bridge 18. It is therefore possible for an individual on bridge 18, and possibly out of view of cab 10, to position himself at will.

The mobile scaffold according to the present invention is conveniently located upon a transporting vehicle as illustrated in FIG. 3. Cab 10 is supported on a main column 96 rotatably supported on bed 98 of a vehicle at the rear end of the bed, that is, at the end of the vehicle remote from ca'b 100, in order to provide storage room for the mobile scaffold according to the present invention. Although placement of cab 10 at the end of bed 98 adjacent the vehicle cab 100 is possible, the described placement at the end of the vehicle remote from cab 100 gives the maximum freedom in manipulating the aparatus, that is, 360 degree freedom in moving the booms. In any case, the booms 14 and 16 are accommodated with boom 16 turned beneath boom 14 on the vehicle bed.

The cab 10 may be turned with respect to bed 98 upon main column 96 which, of course,-has the effect of moving the entire scaffold apparatus in a horizontal arc. Turning of cab 10 is accomplished with motor 106 driving main column 96 by means of chain drive 108. Since booms 14 and 16, as well as the bridge members they carry, are reasonably heavy and are located on a long lever arm, it is desirable that cab 10 be reasonably heavy, particularly in the rear portion 104 thereof in order to provide proper counterweight. During operation of the mobile scaffold according to the present invention, additional support may be desired for the vehicle bed upon which the apparatus may be mounted. For this reason, a hydraulic jack .102 is mounted at each corner of the vehicle bed and may be operated to support the bed directly upon the ground.

The mobile scaffold according to the present invention is effective for providing ready working access to the underside of elevated structures such as bridges, elevated roadways and the like, as shown in FIG. 1. By means of the mobile scaffold according to the present invention, immediate access may be provided to these areas in a minimum amount of time and without installing a semipermanent scaffolding structure. For example, a vehicle, carrying the mobile scaffold, may be moved along roadway 22 to any point where access to the underside of the roadway is desired. The boom 14 is first raised by means of hydraulic cylinder 44 such that intermediate support means 12 and boom 16 may clear the bed 98 of the vehicle. The cab 10 is now turned swinging the booms away from the vehicle, and main shaft 56 is also turned by means of hydraulic motor 84 in order to extend boom 16 away from boom 14. Bridge extension 20 is joined to the bridge 18 as desired. The boom 14 swings the scaffold into a position clearing roadway 22 at the side of the roadway with boom 16 in a position away from the roadway. Now, main cylinder 44 may be controlled to lower boom 14 into a position wherein boom 16 may be swung under the roadway. Hydraulic cylinder 74 is controlled as desired in order to lower boom 16 to the optimum position, and main shaft 56 is further rotated to whatever degree necessary for the positioning of bridge 18 and bridge extension 20 to the proper location. Throughout the operation of the device the intermediate support means 12 as well as bridge 18 and bridge extension 20 are maintained in a substantially parallel attitude with respect to one another and with respect to cab 10. The bridge is thus movable to any desired position without changing its working orientation with its floor parallel to the ground and the working surface.

While the mobile scaffold according to the present invention is particularly useful in providing access to the underside of elevated surfaces and the like, it should also be noted the mobile scaffold can manipulate a working,

bridge or the like into other desired positions and elevations. For example, the mobile scaffold can be employed with the booms 14 and 16 extending in substantially the same direction, as illustrated in FIG. 2, placing bridge 18 and bridge extension 20 at a considerable distance from the cab 10. Moreover, the intermediate support means 12 may be reversed if desired, so that instead of boom 16 depending from the end of boom 14, support means 12 rather extends upwardly from vertical side members 38 to place bridge 18 in a further upraised position.

While I have shown and described a particular embodiment of my invention, it will be apparent to those skilled in the art that many other changes and modifications may be made without departing from my invention in its broader aspects. I therefore intend the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

I claim:

1. A scaffold device comprising:

a base member,

an intermediate support means,

a first boom means extending from said base member to said intermediate support means wherein said first boom means comprises a pair of parallel arm means of substantially equal length pivoted upon said base member on spaced parallel horizontal axes and also pivoted to said intermediate support means on spaced parallel horizontal axes to provide for raising and lowering said first boom means and for movably mounting said intermediate support means in a substantially constant parallel attitude with respect to said base member,

said intermediate support means projecting in a vertical direction from said first boom means,

second boom means pivotally extending from said intermediate support means entirely on the same side of both the spaced horizontal axes on said intermediate support means to which said arm means of said first boom means are pivoted, wherein said second boom means has one end supported by said intermediate support means for rotary movement about a vertical axis with respect to said first boom means and for pivotal movement about a horizontal axis with respect to said intermediate support means to provide for swinging said second boom means about said vertical axis and for raising and lowering said second boom means,

means for raising and lowering said first boom means relative to said base member,

means for raising and lowering said second boom means relative to said intermediate support means,

and means for swinging said second boom means relative to said first boom means.

2. The scaffold device according to claim 1 wherein said base member comprises a rotatable body supported for rotation about a vertical axis.

3. The scatfold device according to claim 1 wherein said intermediate support means comprises a main shaft means maintained in constant vertical orientation by the arm means of said first boom means for rotatably supporting said second boom means.

4. The scaffold device according to claim 1 further including head end means at the end of said second boom means remote from said intermediate support means,

wherein said second boom means comprises first and second parallel arm means of substantially equal length pivoted upon said intermediate support means on parallel axes and pivoting said head end means on parallel axes at the remote end of said parallel arm means maintaining said head end means in a substantially constant parallel attitude with respect to said intermediate support means and said base member.

5. The scafiold device according to claim 4 wherein said head end means comprises a bridge capable of supporting an individual thereon.

6. A mobile scaffold for mounting upon a vehicle comprising a base member for mounting on said vehicle and adapted for rotation with respect to said vehicle around a vertical axis,

intermediate support means,

first boom means extending from said base member to said intermediate support means wherein said first boom means comprises a pair of parallel arms of substantially equal length pivoted for vertical rotation with respect to said base member at one end of said arms and pivoting said intermediate support means for vertical rotation at the remaining end thereof,

said intermediate support means comprising a main shaft maintained in a constant vertical orientation by the arms of said first boom means, said main shaft depending from said first boom means,

said intermediate support means further including means for rotating said main shaft with respect to said first boom means,

second boom means extending from said main shaft at a location thereon below said first boom means, said second boom means comprising first and second parallel arms of substantially equal length pivoted to said main shaft for vertical rotation with respect to said main shaft, bridge means vertically pivotally supported on the remote end of said first and second arms,

actuator means for raising and lowering the said first boom means with respect to said base member, and actuator means for raising and lowering said second boom means with respect to said main shaft.

7. The mobile scaffold according to claim 6 further including an elongated bridge extension for attachment to the bridge at the head end of said second boom means, said bridge extension being maintained in substantially horizontal orientation thereby.

8. The mobile scaffold according to claim 6 wherein at least one arm of said first boom means and one arm of said second boom means each comprise a truss frame having vertical struts for enhancing the structural strength of said boom means.

9. The mobile scaffold according to claim 6 wherein said base member comprises an operating cab rotatably supported at the rear end of the bed of said vehicle spaced from the cab of said vehicle a distance at least equaling the length of said first boom means together with said intermediate support means, said second boom means having a length no longer than said first boom means, so that said first and second boom means may be accommodated longitudinally of said vehicle with said second boom means extending from said intermediate support means under said first boom means toward said base member.

10. The mobile scaffold according to claim 6 further including ,a control station located on said bridge for operating said actuating means.

References Cited UNITED STATES PATENTS 2,674,500 3/1954 Hukari 182-2 3,197,178 7/1965 Nietz l82-63 3,262,517 7/1966 Malec 182-2 FOREIGN PATENTS 933,693 8/ 1963 Great Britain.

REINALDO P. MACHADO, Primary Examiner, 

1. A SCAFFOLD DEVICE COMPRISING: A BASE MEMBER, AN INTERMEDIATE SUPPORT MEANS, A FIRST BOOM MEANS EXTENDING FROM SAID BASE MEMBER TO SAID INTERMEDIATE SUPPORT MEANS WHEREIN SAID FIRST BOOM MEANS COMPRISES A PAIR OF PARALLEL ARM MEANS OF SUBSTANTIALLY EQUAL LENGTH PIVOTED UPON SAID BASE MEMBER ON SPACED PARALLEL HORIZONTAL AXES AND ALSO PIVOTED TO SAID INTERMEDIATE SUPPORT MEANS ON SPACED PARALLEL HORIZONTAL AXES TO PROVIDE FOR RAISING AND LOWERING SAID FIRST BOOM MEANS AND FOR MOVABLY MOUNTING SAID INTERMEDIATE SUPPORT MEANS IN A SUBSTANTIALLY CONSTANT PARALLEL ATTITUDE WITH RESPECT TO SAID BASE MEMBER, SAID INTERMEDIATE SUPPORT MEANS PROJECTING IN A VERTICAL DIRECTION FROM SAID FIRST BOOM MEANS, SECOND BOOM MEANS PIVOTALLY EXTENDING FROM SAID INTERMEDIATE SUPPORT MEANS ENTIRELY ON THE SAME SIDE OF BOTH THE SPACED HORIZONTAL AXES ON SAID INTERMEDIATE SUPPORT MEANS TO WHICH SAID ARM MEANS OF SAID FIRST BOOM MEANS ARE PIVOTED, WHEREIN SAID SECOND BOOM MEANS HAS ONE END SUPPORTED BY SAID INTERMEDIATE SUPPORT MEANS FOR ROTARY MOVEMENT ABOUT A VERTICAL AXIS WITH RESPECT TO SAID FIRST BOOM MEANS AND FOR PIVOTAL MOVEMENT ABOUT A HORIZONTAL AXIS WITH RESPECT TO SAID INTERMEDIATE SUPPORT MEANS TO PROVIDE FOR SWINGING SAID SECOND BOOM MEANS ABOUT SAID VERTICAL AXIS AND FOR RAISING AND LOWERING SAID SECOND BOOM MEANS, MEANS FOR RAISING AND LOWERING SAID FIRST BOOM MEANS RELATIVE TO SAID BASE MEMBER, MEANS FOR RAISING AND LOWERING SAID SECOND BOOM MEANS RELATIVE TO SAID INTERMEDIATE SUPPORT MEANS, AND MEANS FOR SWINGING SAID SECOND BOOM MEANS RELATIVE TO SAID FIRST BOOM MEANS. 